As a rule, mobile phones comprise a plurality of interfaces including connectors for external signals and devices. The phone is usually provided with an interface for RF signals received and transmitted over an external aerial, and with a connector usually coaxial for this purpose, to which a coaxial line from an external aerial is connected. Control or data signals received or transmitted by the phone are transferred via a separate connector. Input and output audio signals frequently have a specific interface and connector. Charging current is supplied to the phone as D.C. supply over a specific connector. FIG. 1 is a schematic view of a typical, well-equipped hand-held mobile phone 1, which, besides its own aerial 1, comprises a coaxial RF connector 3 for input and output RF signals transmitted over an external aerial, a DC connector 4 for power supply and a 12-pin basic connector 5 for external audio, control and data signals.
The invention relates to a digitally operated mobile phone, comprising at least one interface including a connector for RF signals and requiring additional interfaces for at least some output and input digital signals, which may be audio signals, data signals or control signals. Besides these interfaces, a mobile phone requires an interface for supplying charging current. The mobile phone of the invention is particularly advantageous when installed in a car, the hand-held mobile phone being placed in a holder as an independently operating mobile phone, integrated in a versatile car equipment, including for instance a complete loudspeaker feature with an external loudspeaker and a microphone, an interface to an aerial outside the car, interfaces to external data and control signals, such as for instance a signal detecting the state of the ignition switch, an external alarm control, etc., and power supply from the car battery for instance.
Using several connectors in a single mobile phone naturally causes additional expenses, occasionally involving laborious connection of a number of lines. This conventional configuration has the additional drawback of strict protective steps imposed by EMC (Electromagnetic Compatibility ) requirements, both economically and technologically speaking. Electromagnetic protection of the mobile phone lines shall be provided by means of low-pass filters or band-pass filters at the interface of the phone connector. The great number of interfaces and connectors complicates the phone design considerably, calling for several filter components in the phone and entailing laborious and complicated manufacture. What is more, this kind of filter arrangement requires space in the phone set and will thus increase the weight and the size of the phone.
With some interfaces, for instance with a data interface, the transfer rate will not comply with EMC requirements. In that case it might be necessary to use an optical interface, which, again, requires large space and separate operating voltage.